The fortified stronghold at the centre of the Castle. Originally all the living quarters and stores were also in the Keep.
The external wall of the Castle. The sea-ward side is in its original position, but the northern side was completely rebuilt in 1814 to extend the Castle and provide living quarters for a larger garrison of 200 men.
The line of the original Tudor wall can be seen in the courtyard in the area adjacent to the well.
A gallery running around the moat. This feature was added in 1814.
A bomb-proof passage under the moat leading from the inside of the Castle into the Counterscarp Gallery.
An earthwork on the outside of the moat sloping gradually from the top of the moat to ground level. This feature reduced the target area of the Castle for enemy gunners and was added in the late 17th century. The shape of the glacis has been lost in later 19th century work to add flanking batteries on either side of the Castle.
Added in 1820s to aid navigation for vessels using the deep water channels. It is still in use today and plays a central role in the navigational system for ships entering Portsmouth Harbour.